shell 環境

As we discussed earlier, the shell maintains a body of information during our shell session called the environment. Data stored in the environment is used by programs to determine facts about our configuration. While most programs use configuration files to store program settings, some programs will also look for values stored in the environment to adjust their behavior. Knowing this, we can use the environment to customize our shell experience.

恰如我們之前所講的，shell 在 shell 會話中儲存著大量資訊。這些資訊被稱為 (shell 的) 環境。 程式獲取環境中的資料（即環境變數）來了解本機的配置。雖然大多數程式用配置檔案來儲存程式設定， 一些程式會根據環境變數來調整他們的行為。知道了這些，我們就可以用環境變數來自訂製 shell 體驗。

In this chapter, we will work with the following commands:

• printenv – Print part or all of the environment

• set – Set shell options

• export – Export environment to subsequently executed programs

• alias – Create an alias for a command

在這一章，我們將用到以下命令：

• printenv - 列印部分或所有的環境變數

• set - 設定 shell 選項

• export — 匯出環境變數，讓隨後執行的程式知道。

• alias - 建立命令別名

什麼儲存在環境變數中？

The shell stores two basic types of data in the environment, though, with bash, the types are largely indistinguishable. They are environment variables and shell variables. Shell variables are bits of data placed there by bash, and environment variables are basically everything else. In addition to variables, the shell also stores some programmatic data, namely aliases and shell functions. We covered aliases in Chapter 6, and shell functions (which are related to shell scripting) will be covered in Part 5.

shell 在環境中儲存了兩種基本型別的資料，雖然 bash 幾乎無法分辨這些資料的型別。 它們是環境變數和 shell 變數。Shell 變數是 bash 存放的少量資料。剩下的都是 環境變數。除了變數，shell 也儲存了一些可程式設計的資料，即別名和 shell 函式。我們 已經在第六章討論了別名，而 shell 函式（涉及到 shell 指令碼）將會在本章第五部分敘述。

檢查環境變數

We can use either the set builtin in bash or the printenv program to see what is stored in the environment. The set command will show both the shell and environment variables, while printenv will only display the latter. Since the list of environment contents will be fairly long, it is best to pipe the output of either command into less:

我們可以用 bash 的內建命令 set，或者是 printenv 程式來檢視環境變數。set 命令可以 顯示 shell 或環境變數，而 printenv 只是顯示環境變數。因為環境變數列表比較長，最好 把每個命令的輸出透過管道傳遞給 less 來閱讀：

[me@linuxbox ~]$ printenv | less

Doing so, we should get something that looks like this:

執行以上命令之後，我們應該能得到類似以下內容：

KDE_MULTIHEAD=false
SSH_AGENT_PID=6666
HOSTNAME=linuxbox
GPG_AGENT_INFO=/tmp/gpg-PdOt7g/S.gpg-agent:6689:1
SHELL=/bin/bash
TERM=xterm
XDG_MENU_PREFIX=kde-
HISTSIZE=1000
XDG_SESSION_COOKIE=6d7b05c65846c3eaf3101b0046bd2b00-1208521990.996705
-1177056199
GTK2_RC_FILES=/etc/gtk-2.0/gtkrc:/home/me/.gtkrc-2.0:/home/me/.kde/sh
are/config/gtkrc-2.0
GTK_RC_FILES=/etc/gtk/gtkrc:/home/me/.gtkrc:/home/me/.kde/share/confi
g/gtkrc
GS_LIB=/home/me/.fonts
WINDOWID=29360136
QTDIR=/usr/lib/qt-3.3
QTINC=/usr/lib/qt-3.3/include
KDE_FULL_SESSION=true
USER=me
LS_COLORS=no=00:fi=00:di=00;34:ln=00;36:pi=40;33:so=00;35:bd=40;33;01
:cd=40;33;01:or=01;05;37;41:mi=01;05;37;41:ex=00;32:\*.cmd=00;32:\*.exe:

What we see is a list of environment variables and their values. For example, we see a variable called USER, which contains the value “me”. The printenv command can also list the value of a specific variable:

我們所看到的是環境變數及其數值的列表。例如，我們看到一個叫做 USER 的變數，這個變數值是 “me”。printenv 命令也能夠列出特定變數的數值：

[me@linuxbox ~]$ printenv USER
me

The set command, when used without options or arguments, will display both the shell and environment variables, as well as any defined shell functions. Unlike printenv, its output is courteously sorted in alphabetical order:

當使用沒有帶選項和引數的 set 命令時，shell 變數，環境變數，和定義的 shell 函式 都會被顯示。不同於 printenv 命令，set 命令的輸出很友好地按照首字母順序排列：

[me@linuxbox ~]$ set | less

It is also possible to view the contents of a variable using the echo command, like this:

也可以透過 echo 命令來檢視一個變數的內容，像這樣：

[me@linuxbox ~]$ echo $HOME
/home/me

One element of the environment that neither set nor printenv displays is aliases. To see them, enter the alias command without arguments:

別名無法透過使用 set 或 printenv 來檢視。 用不帶引數的 alias 來檢視別名:

[me@linuxbox ~]$ alias
alias l.='ls -d .* --color=tty'
alias ll='ls -l --color=tty'
alias ls='ls --color=tty'
alias vi='vim'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'

一些有趣的環境變數

The environment contains quite a few variables, and though your environment may differ from the one presented here, you will likely see the following variables in your environment:

shell 環境中包含相當多的變數。雖然你的 shell 環境可能與這裡的不同，你可能會看到 以下的環境變數：

Don’t worry if some of these values are missing. They vary by distribution.

如果缺失了一些變數，不要擔心，這些變數會因發行版本的不同而不同。

如何建立 shell 環境？

When we log on to the system, the bash program starts, and reads a series of configuration scripts called startup files, which define the default environment shared by all users. This is followed by more startup files in our home directory that define our personal environment. The exact sequence depends on the type of shell session being started. There are two kinds: a login shell session and a non-login shell session.

當我們登入系統後， bash 程式啟動，並且會讀取一系列稱為啟動檔案的配置指令碼， 這些檔案定義了預設的可供所有使用者共享的 shell 環境。然後是讀取更多位於我們自己家目錄中 的啟動檔案，這些啟動檔案定義了使用者個人的 shell 環境。確切的啟動順序依賴於要執行的 shell 會話 型別。有兩種 shell 會話型別：一個是登入 shell 會話，另一個是非登入 shell 會話。

A login shell session is one in which we are prompted for our user name and password; when we start a virtual console session, for example. A non-login shell session typically occurs when we launch a terminal session in the GUI.

登入 shell 會話會在其中提示使用者輸入使用者名稱和密碼；例如，我們啟動一個虛擬控制檯會話。 非登入 shell 會話通常當我們在 GUI 下啟動終端會話時出現。

Login shells read one or more startup files as shown in Table 12-2:

登入 shell 會讀取一個或多個啟動檔案，正如表12－2所示：

Non-login shell sessions read the following startup files:

非登入 shell 會話會讀取以下啟動檔案：

In addition to reading the startup files above, non-login shells also inherit the environment from their parent process, usually a login shell.

除了讀取以上啟動檔案之外，非登入 shell 會話也會繼承它們父程序的環境設定，通常是一個登入 shell。

Take a look at your system and see which of these startup files you have. Remember— since most of the filenames listed above start with a period (meaning that they are hidden), you will need to use the “-a” option when using ls.

瀏覽一下你的系統，看一看系統中有哪些啟動檔案。記住－因為上面列出的大多數檔名都以圓點開頭 （意味著它們是隱藏檔案），你需要使用帶”-a”選項的 ls 命令。

The ~/.bashrc file is probably the most important startup file from the ordinary user’s point of view, since it is almost always read. Non-login shells read it by default and most startup files for login shells are written in such a way as to read the ~/.bashrc file as well.

在普通使用者看來，檔案 ~/.bashrc 可能是最重要的啟動檔案，因為它幾乎總是被讀取。非登入 shell 預設 會讀取它，並且大多數登入 shell 的啟動檔案會以能讀取 ~/.bashrc 檔案的方式來書寫。

一個啟動檔案的內容

If we take a look inside a typical .bash_profile (taken from a CentOS 4 system), it looks something like this:

如果我們看一下典型的 .bash_profile 檔案（來自於 CentOS 4 系統），它看起來像這樣：

# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
PATH=$PATH:$HOME/bin
export PATH

Lines that begin with a “#” are comments and are not read by the shell. These are there for human readability. The first interesting thing occurs on the fourth line, with the following code:

以”#”開頭的行是註釋，shell 不會讀取它們。它們在那裡是為了方便人們閱讀。第一件有趣的事情 發生在第四行，伴隨著以下程式碼：

if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi

This is called an if compound command, which we will cover fully when we get to shell scripting in Part 5, but for now we will translate:

這叫做一個 if 複合命令，我們將會在第五部分詳細地介紹它，現在我們對它翻譯一下：

If the file ~/.bashrc exists, then
read the ~/.bashrc file.

We can see that this bit of code is how a login shell gets the contents of .bashrc. The next thing in our startup file has to do with the PATH variable.

我們可以看到這一小段程式碼就是一個登入 shell 得到 .bashrc 檔案內容的方式。在我們啟動檔案中， 下一件有趣的事與 PATH 變數有關係。

Ever wonder how the shell knows where to find commands when we enter them on the command line? For example, when we enter ls, the shell does not search the entire computer to find /bin/ls (the full pathname of the ls command), rather, it searches a list of directories that are contained in the PATH variable.

是否曾經對 shell 怎樣知道在哪裡找到我們在命令列中輸入的命令感到迷惑？例如，當我們輸入 ls 後， shell 不會查詢整個計算機系統來找到 /bin/ls（ls 命令的全路徑名），相反，它查詢一個目錄列表， 這些目錄包含在 PATH 變數中。

The PATH variable is often (but not always, depending on the distribution) set by the /etc/profile startup file and with this code:

PATH 變數經常（但不總是，依賴於發行版）在 /etc/profile 啟動檔案中設定，透過這些程式碼：

PATH=$PATH:$HOME/bin

PATH is modified to add the directory $HOME/bin to the end of the list. This is an example of parameter expansion, which we touched on in Chapter 8. To demonstrate how this works, try the following:

修改 PATH 變數，新增目錄 $HOME/bin 到目錄列表的末尾。這是一個引數展開的範例， 引數展開我們在第八章中提到過。為了說明這是怎樣工作的，試試下面的例子：

[me@linuxbox ~]$ foo="This is some"
[me@linuxbox ~]$ echo $foo
This is some
[me@linuxbox ~]$ foo="$foo text."
[me@linuxbox ~]$ echo $foo
This is some text.

Using this technique, we can append text to the end of a variable’s contents. By adding the string $HOME/bin to the end of the PATH variable’s contents, the directory $HOME/bin is added to the list of directories searched when a command is entered. This means that when we want to create a directory within our home directory for storing our own private programs, the shell is ready to accommodate us. All we have to do is call it bin, and we’re ready to go.

使用這種技巧，我們可以把文字附加到一個變數值的末尾。透過新增字串 $HOME/bin 到 PATH 變數值 的末尾，則目錄 $HOME/bin 就新增到了命令搜尋目錄列表中。這意味著當我們想要在自己的家目錄下， 建立一個目錄來儲存我們自己的私人程式時，shell 已經給我們準備好了。我們所要做的事就是 把建立的目錄叫做 bin，趕快行動吧。

Note: Many distributions provide this PATH setting by default. Some Debian based distributions, such as Ubuntu, test for the existence of the ~/bin directory at login, and dynamically add it to the PATH variable if the directory is found.

注意：很多發行版預設地提供了這個 PATH 設定。一些基於 Debian 的發行版，例如 Ubuntu，在登入 的時候，會檢測目錄 ~/bin 是否存在，若找到目錄則把它動態地加到 PATH 變數中。

Lastly, we have:

最後，有下面一行程式碼：

export PATH

The export command tells the shell to make the contents of PATH available to child processes of this shell.

這個 export 命令告訴 shell 讓這個 shell 的子程序可以使用 PATH 變數的內容。

修改 shell 環境

Since we know where the startup files are and what they contain, we can modify them to customize our environment.

既然我們知道了啟動檔案所在的位置和它們所包含的內容，我們就可以修改它們來訂製自己的 shell 環境。

我們應該修改哪個檔案？

As a general rule, to add directories to your PATH, or define additional environment variables, place those changes in .bash_profile (or equivalent, according to your distribution. For example, Ubuntu uses .profile.) For everything else, place the changes in .bashrc. Unless you are the system administrator and need to change the defaults for all users of the system, restrict your modifications to the files in your home directory. It is certainly possible to change the files in /etc such as profile, and in many cases it would be sensible to do so, but for now, Let's play it safe.

按照通常的規則，新增目錄到你的 PATH 變數或者是定義額外的環境變數，要把這些更改放置到 .bash_profile 檔案中（或者其替代檔案中，根據不同的發行版。例如，Ubuntu 使用 .profile 檔案）。 對於其它的更改，要放到 .bashrc 檔案中。除非你是系統管理員，需要為系統中的所有使用者修改 預設設定，那麼則限定你只能對自己家目錄下的檔案進行修改。當然，有可能會更改 /etc 目錄中的 檔案，比如說 profile 檔案，而且在許多情況下，修改這些檔案也是明智的，但是現在，我們要謹慎行事。

文字編輯器

To edit (i.e., modify) the shell’s startup files, as well as most of the other configuration files on the system, we use a program called a text editor. A text editor is a program that is, in some ways, like a word processor in that it allows you to edit the words on the screen with a moving cursor. It differs from a word processor by only supporting pure text, and often contains features designed for writing programs. Text editors are the central tool used by software developers to write code, and by system administrators to manage the configuration files that control the system.

為了編輯（例如，修改）shell 的啟動檔案以及系統中大多數其它配置檔案，我們使用一個叫做文字編輯器的程式。 文字編輯器是一個在某些方面類似於文書處理器的程式，允許你使用移動游標在螢幕上編輯文字。 文字編輯器不同於文書處理器之處在於它只能支援純文字，並且經常包含為便於寫程式而設計的特性。 文字編輯器是軟體開發人員用來寫程式碼，以及系統管理員用來管理控制系統的配置檔案的重要工具。

There are a lot of different text editors available for Linux; your system probably has several installed. Why so many different ones? Probably because programmers like writing them, and since programmers use them extensively, they write editors to express their own desires as to how they should work.

Linux 系統有許多不同型別的文字編輯器可用；你的系統中可能已經安裝了幾個。為什麼會有這麼 多種呢？可能因為程式設計師喜歡編寫它們，又因為程式設計師們會頻繁地使用它們，所以程式設計師編寫編輯器讓 它們按照程式設計師自己的願望工作。

Text editors fall into two basic categories: graphical and text based. GNOME and KDE both include some popular graphical editors. GNOME ships with an editor called gedit, which is usually called “Text Editor” in the GNOME menu. KDE usually ships with three which are (in order of increasing complexity) kedit, kwrite, and kate.

文字編輯器分為兩種基本型別：圖形化的和基於文字的編輯器。GNOME 和 KDE 兩者都包含一些流行的 圖形化編輯器。GNOME 自帶了一個叫做 gedit 的編輯器，這個編輯器通常在 GNOME 選單中稱為”文字編輯器”。 KDE 通常自帶了三種編輯器，分別是（按照複雜度遞增的順序排列）kedit，kwrite，kate。

There are many text-based editors. The popular ones you will encounter are nano, vi, and emacs. The nano editor is a simple, easy-to-use editor designed as a replacement for the pico editor supplied with the PINE email suite. The vi editor (on most Linux systems replaced by a program named vim, which is short for “Vi IMproved”) is the traditional editor for Unix-like systems. It will be the subject of our next chapter. The emacs editor was originally written by Richard Stallman. It is a gigantic, all-purpose, does-everything programming environment. While readily available, it is seldom installed on most Linux systems by default.

有許多基於文字的編輯器。你將會遇到一些流行的編輯器，它們是 nano、vi和 emacs。 nano 編輯器 是一個簡單易用的編輯器，用於替代隨 PINE 郵件套件提供的 pico 編輯器。vi 編輯器 （在大多數 Linux 系統中被 vim 替代，vim 是 “Vi IMproved”的簡寫）是類別 Unix 作業系統的傳統編輯器。 vim 是我們下一章節的討論物件。emacs 編輯器最初由 Richard Stallman 寫成。它是一個龐大、多用途的， 可做任何事情的程式設計環境。雖然 emacs 很容易獲取，但是大多數 Linux 系統很少預設安裝它。

使用文字編輯器

All text editors can be invoked from the command line by typing the name of the editor followed by the name of the file you want to edit. If the file does not already exist, the editor will assume that you want to create a new file. Here is an example using gedit:

所有的文字編輯器都可以透過在命令列中輸入編輯器的名字，加上你所想要編輯的檔案來喚醒。如果所 輸入的檔名不存在，編輯器則會假定你想要建立一個新檔案。下面是一個使用 gedit 的例子：

[me@linuxbox ~]$ gedit some_file

This command will start the gedit text editor and load the file named “some_file”, if it exists.

這條命令將會啟動 gedit 文字編輯器，同時載入名為 “some_file” 的檔案，如果這個檔案存在的話。

All graphical text editors are pretty self-explanatory, so we won’t cover them here. Instead, we will concentrate on our first text-based text editor, nano. Let's fire up nano and edit the .bashrc file. But before we do that, Let's practice some “safe computing.” Whenever we edit an important configuration file, it is always a good idea to create a backup copy of the file first. This protects us in case we mess the file up while editing. To create a backup of the .bashrc file, do this:

所有的圖形文字編輯器很大程度上都是不需要解釋的，所以我們在這裡不會介紹它們。反之，我們將集中精力在 我們第一個基於文字的文字編輯器，nano。讓我們啟動 nano，並且編輯檔案 .bashrc。但是在我們這樣 做之前，先練習一些”安全計算”。當我們編輯一個重要的配置檔案時，首先建立一個這個檔案的備份 總是一個不錯的主意。這樣能避免我們在編輯檔案時弄亂檔案。建立檔案 .bashrc 的備份檔案，這樣做：

[me@linuxbox ~]$ cp .bashrc .bashrc.bak

It doesn’t matter what you call the backup file, just pick an understandable name. The extensions “.bak”, “.sav”, “.old”, and “.orig” are all popular ways of indicating a backup file. Oh, and remember that cp will overwrite existing files silently.

備份檔案的名字無關緊要，只要選擇一個容易理解的檔名。副檔名 “.bak”、”.sav”、 “.old”和 “.orig” 都是用來指示備份檔案的流行方法。哦，記住 cp 命令會默默地覆蓋已經存在的同名檔案。

Now that we have a backup file, we’ll start the editor:

現在我們有了一個備份檔案，我們啟動 nano 編輯器吧：

[me@linuxbox ~]$ nano .bashrc

Once nano starts, we’ll get a screen like this:

一旦 nano 編輯器啟動後，我們將會得到一個像下面一樣的螢幕：

GNU nano 2.0.3
....

Note: If your system does not have nano installed, you may use a graphical editor instead.

注意：如果你的系統中沒有安裝 nano 編輯器，你可以用一個圖形化的編輯器代替。

The screen consists of a header at the top, the text of the file being edited in the middle and a menu of commands at the bottom. Since nano was designed to replace the text editor supplied with an email client, it is rather short on editing features. The first command you should learn in any text editor is how to exit the program. In the case of nano, you type Ctrl-x to exit. This is indicated in the menu at the bottom of the screen. The notation “^X” means Ctrl-x. This is a common notation for control characters used by many programs.

這個螢幕由上面的標頭，中間正在編輯的檔案文字和下面的命令選單組成。因為設計 nano 是為了 代替由電子郵件客戶端提供的編輯器的，所以它相當缺乏編輯特性。在任一款編輯器中，你應該 學習的第一個命令是怎樣退出程式。以 nano 為例，你輸入 Ctrl-x 來退出 nano。在螢幕底層的選單中 說明了這個命令。”^X” 表示法意思是 Ctrl-x。這是控制字元的常見表示法，許多程式都使用它。

The second command we need to know is how to save our work. With nano it’s Ctrl- o. With this knowledge under our belts, we’re ready to do some editing. Using the down arrow key and / or the PageDown key, move the cursor to the end of the file, then add the following lines to the .bashrc file:

第二個我們需要知道的命令是怎樣儲存我們的勞動成果。對於 nano 來說是 Ctrl-o。既然我們 已經獲得了這些知識，接下來我們準備做些編輯工作。使用下箭頭按鍵和 / 或下翻頁按鍵，移動 滑鼠到檔案的最後一行，然後新增以下幾行到檔案 .bashrc 中：

umask 0002
export HISTCONTROL=ignoredups
export HISTSIZE=1000
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'

Note: Your distribution may already include some of these, but duplicates won’t hurt anything.

注意：你的發行版在這之前可能已經包含其中的一些行，出現重複的程式碼不會有其他影響。

Here is the meaning of our additions:

下表是所新增行的意義：

As we can see, many of our additions are not intuitively obvious, so it would be a good idea to add some comments to our .bashrc file to help explain things to the humans. Using the editor, change our additions to look like this:

正如我們所看到的，我們新增的許多程式碼的意思直覺上並不是明顯的，所以添加註釋到我們的檔案 .bashrc 中是 一個好主意，可以幫助人們理解。使用編輯器，更改我們新增的程式碼，讓它們看起來像這樣：

# Change umask to make directory sharing easier
umask 0002
 # Ignore duplicates in command history and increase
 # history size to 1000 lines
export HISTCONTROL=ignoredups
export HISTSIZE=1000
 # Add some helpful aliases
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'

Ah, much better! With our changes complete, type Ctrl-o to save our modified .bashrc file, and Ctrl-x to exit nano.

啊，看起來好多了! 當我們完成修改後，輸入 Ctrl-o 來儲存我們修改的 .bashrc 檔案，輸入 Ctrl-x 退出 nano。

Why Comments Are Important

為什麼註釋很重要？

Whenever you modify configuration files it’s a good idea to add some comments to document your changes. Sure, you will remember what you changed tomorrow, but what about six months from now? Do yourself a favor and add some comments. While you’re at it, it’s not a bad idea to keep a log of what changes you make.

不管什麼時候你修改配置檔案時，給你所做的更改加上註釋都是一個好主意。的確，明天你會 記得你修改了的內容，但是六個月之後會怎樣呢？幫自己一個忙，加上一些註釋吧。當你意識 到這一點後，對你所做的修改做個日誌是個不錯的主意。

Shell scripts and bash startup files use a “#” symbol to begin a comment. Other configuration files may use other symbols. Most configuration files will have comments. Use them as a guide.

Shell 指令碼和 bash 啟動檔案都使用「#」符號來開始註釋。其它配置檔案可能使用其它的符號。 大多數配置檔案都有註釋。把它們作為指南。

You will often see lines in configuration files that are commented out to prevent them from being used by the affected program. This is done to give the reader suggestions for possible configuration choices or examples of correct configuration syntax. For example, the .bashrc file of Ubuntu 8.04 contains these lines:

你會經常看到配置檔案中的一些行被註釋掉，以此防止它們被受影響的程式使用。這樣做 是為了給讀者在可能的配置選項方面一些建議，或者給出正確的配置語法範例。例如，Ubuntu 8.04 中的 .bashrc 檔案包含這些行：

# some more ls aliases
#alias ll='ls -l'
#alias la='ls -A'
#alias l='ls -CF'

The last three lines are valid alias definitions that have been commented out. If you remove the leading “#” symbols from these three lines, a technique called uncommenting, you will activate the aliases. Conversely, if you add a “#” symbol to the beginning of a line, you can deactivate a configuration line while preserving the information it contains.

最後三行是有效的被註釋掉的別名定義。如果你刪除這三行開頭的「#」符號，此技術程稱為 uncommenting (取消註釋)，這樣你就會啟用這些別名。相反地，如果你在一行的開頭加上「#」符號， 你可以登出掉這一行，但會保留它所包含的資訊。

啟用我們的修改

The changes we have made to our .bashrc will not take affect until we close our terminal session and start a new one, since the .bashrc file is only read at the beginning of a session. However, we can force bash to re-read the modified .bashrc file with the following command:

我們對於檔案 .bashrc 的修改不會生效，直到我們關閉終端會話，再重新啟動一個新的會話， 因為 .bashrc 檔案只是在剛開始啟動終端會話時讀取。然而，我們可以強迫 bash 重新讀取修改過的 .bashrc 檔案，使用下面的命令：

[me@linuxbox ~]$ source .bashrc

After doing this, we should be able to see the effect of our changes. Try out one of the new aliases:

執行上面命令之後，我們就應該能夠看到所做修改的效果了。試試其中一個新的別名：

[me@linuxbox ~]$ ll

總結

In this chapter we learned an essential skill—editing configuration files with a text editor. Moving forward, as we read man pages for commands, take note of the environment variables that commands support. There may be a gem or two. In later chapters, we will learn about shell functions, a powerful feature that you can also include in the bash startup files to add to your arsenal of custom commands.

在這一章中，我們學到了用文字編輯器來編輯配置檔案的基本技巧。隨著學習的繼續，當我們 瀏覽命令的手冊頁時，可以記錄下該命令所支援的環境變數。這樣或許我們能夠收穫一到兩個特別好用的寶貝命令。 在隨後的章節裡面，我們將會學習 shell 函式，一個很強大的特性，你可以把它包含在 bash 啟動檔案裡面， 以此來新增你自訂製的命令寶函式庫。

拓展閱讀

The INVOCATION section of the bash man page covers the bash startup files in gory detail.

bash 手冊頁的 INVOCATION 部分非常詳細地討論了 bash 啟動檔案。